\Hip`po*cam"pus\, n. [L., the sea horse, Gr. ? a
hippocampus (in senses 1 and 2); "i`ppos horse + ? to bend.]
1. (Class. Myth.) A fabulous monster, with the head and fore
   quarters of a horse joined to the tail of a dolphin or
   other fish ({Hippocampus brevirostris}), -- seen in
   Pompeian paintings, attached to the chariot of Neptune.
   --Fairholt.
2. (Zo["o]l.) A genus of lophobranch fishes of several
   species in which the head and neck have some resemblance
   to those of a horse; -- called also {sea horse}.
Note: They swim slowly, in an erect position, and often cling
      to seaweeds by means of the incurved prehensile tail.
      The male has a ventral pouch, in which it carries the
      eggs till hatched.
3. (Zo["o]l.) A name applied to either of two ridges of white
   matter in each lateral ventricle of the brain. The larger
   is called hippocampus major or simply hippocampus. The
   smaller, hippocampus minor, is called also {ergot} and
   {calcar}.